Boulder officials have released the city's preliminary assessment of flood damage to infrastructure, parks and open space: $48.91 million.

But the numbers are expected to rise as waters continue to recede.

The figure, provided to the Federal Emergency Management Agency on Thursday, covers only the public infrastructure that city work crews have been able to access since the end of the heavy rainstorms that caused Boulder's 100-year flood two weeks ago, officials say.

According to the city, FEMA has also been made aware that some Boulder properties remain under water.

"These numbers are going to change," city spokesman Patrick von Keyserling said. "The numbers are likely to increase as staff continue to gain access to areas that are currently under water or under debris."

The city property most heavily damaged, according to the assessment, is open space and mountain parks. Those areas suffered an estimated $17.67 million in flooding impacts. About 93 miles, or 64 percent, of the city's 145 miles of trails suffered significant to severe damage, according to the city.

While work including replacing trails, water delivery infrastructure and fencing are needed in many areas, Boulder's Open Space and Mountain Parks Department did reopen a few more trails Thursday, as it has been doing throughout the week.

A man photographs the flooding in the underpass at Boulder Creek and Broadway on Sept. 12, 2013/ (Cliff Grassmick / Daily Camera)

Those included Prairie Vista, Flatirons Vista North and a portion of the Flatirons Vista South trails, despite the Flatirons Vista trailhead remaining closed. The Marshall Mesa trailhead and all associated trails, save for the High Plains Trail, were also reopened, as was the first/second Flatiron Trail, though the area remains closed to climbing, according to the city.

About one-third of the city's trails are now open between dawn and dusk each day.

Boulder's parks and recreation infrastructure was also affected by flooding. According to preliminary assessments, $2.39 million in damage was done to parks and recreation facilities, 35 of which suffered significant damage.

The city's water, wastewater and stormwater utilities systems all suffered millions of dollars in assessed damage.

An estimated $3.3 million will be needed to repair water utilities, including restoring areas that were eroded by floodwaters and are now jeopardizing the path of critical water delivery pipelines, according to the city.

About 25 percent of the pipes in the city's 400-mile sanitary sewer system must be inspected and cleaned, at an estimated cost of $2.5 million, officials say.

Meanwhile, the city's stormwater utility sustained an estimated $13.85 million in flood-related damage, and all 160 miles of pipe in the system must be inspected and cleaned. "Vast amounts of sediment and debris" must be removed from the system, according to the city, and reconstruction including improved drainageway features will be required.

So far, estimated damage to the Boulder's transportation infrastructure is only being assessed at $6 million. Just three miles, or 1 percent, of the city's roads were found to be damaged by the flood, though an estimated 60 miles of road were covered in debris. Nine miles of bike paths in the city were damaged, according to the assessment.

Von Keyserling said transportation is one area where he expects the assessment to rise. He said many underpasses and multi-use paths around Boulder are still covered in mud or obstructed by debris.

"Once those things are removed, then crews will be able to assess the damage to the actual infrastructure," he said.

Another $3.2 million in damage has been assessed at city buildings and structures. While 59 utilities and parking structures must still be inspected, 35 of the other 306 structures owned by the city have some damage.

FEMA spokesman Bill Rukeyser said he did not have Boulder-specific numbers of people who requested assistance with damage to their residences. So far, 11,721 households in Boulder County have contacted FEMA for assistance, whether it be for damaged homes, damaged property or loss of income as a result of the flooding.

FEMA had approved $17.5 million in assistance to Boulder County residents by the end of business Wednesday, Rukeyser said.

Longmont released its own preliminary assessment Tuesday night of the city's infrastructure damage, estimating it at $148.6 million.

Boulder officials say they are working with local, state and federal authorities to ensure all infrastructure repairs are performed in accordance with FEMA guidelines.

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